1. has been done before. works.
see here...
2. as mentioned: 75 Kilos is max load while driving. Going through (heavy) terrain, it's reduced to 50 Kilos. stationary a couple of hundret kilos are no prob. However, that's LRs "we're affraid of getting sued" communication-policy. but on their on experience tours, they load more than those 75 Kilos onto the roofs of their own evoques
see for example here (silk road tour)
- Mind you, they're using three instead of two crossbars (for a reason). -
3. I'm pretty sure that cars with panorama roof do have a more stable roof, than those without. The frame that holds the panorama adds strength and the glass itself is way more rigidity than a thin metallsheet...
4. from my own experience i can tell you, that driving offroad (partly harsh) with aprox 60 Kilos on the roof isn't a problem for the evoque.
as you can see here...
5. have a look on "james baroud" tents. similar pricing but imho better quality and detailing on the finish
http://www.jamesbaroud.org/
rgds
flo